• 전기의세계
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• v.26 no.4
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• pp.61-67
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• 1977

This paper treats the Ultrasonic effects on the break down characteristics of Liquid Dielectric Material 1) Relative Dielectric constant, Es of Liquid Dielectric Material at a constant temperature decreases in proportion to the irradiated time of Ultrasonic radiation and its intensity, and reaches to a certain saturated value. The saturated value varies with the intensity of Ultrasonic radiation. 2) Power factor of Liquid Dielectric Material at a constant temperature increases in proportion tothe irradiated time of Ultrasonic radiation and its intensity, and reaches to a certain saturated value. The saturated value varies with the intensity of Ultrasonic radiation. 3) Relative resistance of Liquid Dielectric Material at a constant temperature decrease with the irradiated time of Ultrasonic radiation, but the effect of its intensity is very irregular. 4) Break-down strength of Liquid Dielectric Material, at a constant temperature decreases with the irradiated time of Ultrasonic radiation and its intensity, and then reaches to a saturated value.

• Korean Journal of Crystallography
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• v.14 no.1
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• pp.24-24
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• 2003

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1382-1387
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• 1994

A model is constructed to evaluate the stress intensity factors for a center crack subjected to anti-symmetric loading in a layered material. A Fredholm integral equation is derived using the Fourier integral transform method. The integral equation is numerically analyzed to evaluate the effects of stress intensity factor on the shear modulus, Poisson's ratio and crack length to layer thickness. In case of the isotropic homogeneous material, the values of stress intensity factor derived in the present study agree with the previous solutions.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.10a
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• pp.194-197
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• 1996

The high-strength aluminum alloy 7075-T651 was used to observe the fatigue-crack-propagation behavior for the various stress ratios with constant amplitude loading and thus to predict the fatigue life. With a chevron notch in the specimen the fatigue-crack-propagation behavior of through crack was investigated. Crack propagation behavior of through crack in the depth direction and crack growth of weldments were experimentally studied. Base material heat affected zone and weld material were considered in the fracture of weldments. The change of crack-propagation length with respect to several parameters such as stress intensity factor range(ΔK) effective stress intensity factor range(ΔKeff)ration of effective stress intensity factor range(U) stress intensity factor of crack opening point(K op) maximum stress intensity factor(K max) and number of cycles(Nf)was determined. The crack length of through crack of weldments was 2.4mm and the remaining part was a base material. The experiment was accomplished by making the crack propagate near the base material.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3219-3226
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• 1994

A model is constructed to evaluate the stress intensity factors for a center crack subjected to polynomial anti-symmetric loading in a layered material. A Fredholm integral equation is derived by Fourier integral transform method. The integral equation is numerically analyzed to evaluate the effects of the ratios of shear modulus, Poisson's ratio and crack length to layer thickness as well as the number of layers on the stress intensity factor. The stress intensity factors are approached to constant values as the number of layers increase and decrease as the polynomial power of the loading increase. In case of the E-glass/Epoxy composite, dimensionless stress intensity factor is affected by cracked-resin layer thickness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.149-156
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• 2012

In fracture mechanics, the weight function can be used for calculating stress intensity factors. In this paper, a two-dimensional electroelastic analysis is performed on a transversely isotropic piezoelectric material with an open crack. A plane strain formulation of the piezoelectric problem is solved within the Leknitskii formalism. Weight function theory is extended to piezoelectric materials. The stress intensity factors and electric displacement intensity factor are calculated by the weight function theory.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1705-1712
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• 1994

Hilbert problems are derived to evaluate thermal stress intensity factors for a partially insulated crack subjected to vertically uniform heat flow in infinite bonded dissimilar materials. In case of fully insulated crack surface, the present solutions of thermal stress intensity factors are reduced into the same as the previous results. For the homogeneous material, mode II thermal stress intensity factor only exists. However, in the bonded dissimilar materials, both mode I and II thermal stress intensity factors are obtained. Specially, in this case, mode II thermal stress intensity factor is dominent. Also, thermal stress intensity factors are strongly influenced by the material properties. Thermal stress intensity factors decrease when the degree of insulation decreases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.359-370
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• 1993

Up to now, most studies are on interface crack problems in isotropic-isotropic dissimilar materials, but it seems to be not so much on anisotropic dissimlar materials. In this study, the stress intensity factors for an interface crack in anisotropic dissimilar materials are analysed using author's proposed extrapolation method by BEM and we have done a parametric study about material properties or shapes of crack affecting to the stress intensity factors. However, as there are not other's comparable numerical results on these anisotropic dissimilar materials to the best of author's knowledge, the reliability of the present results was proved by following two methods. The first is considering the asymptotic characteristic about stress intensity factors for an interface crack in anisotropic materials when the ansiotropic material approachs to the isotropic material. The second is considering the discontinuity of stress intensity factors between of a crack in an identical homogeneous anisotropic material and an interface crack in anisotropic dissimilar materials.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.1904-1911
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• 1999

The most effective material in the shape memory alloy(SMA) is the TiNi alloy, because its shape recovery characteristics are very excellent. We molded the composite material with shape memory function. The fiber of it is $Ti_{50}-Ni_{50}$ shape memory alloy and matrix of it is epoxy resin(Araldite B41, Hardner HT903. Ciba Geigy), its adhesive and optical sensitivity are very excellent. It was assured that the composite material could be used as model material of photoelastic experiment for intelligent materials or structures. In this research, the composite material with shape memory function is used as model material of photoelastic experiment. Photoelastic experimental hybrid method is developed in this research, it is assured that it is useful on the obtaining stress intensity factor and the separation of stress components from only isochromatic data. The measuring method of stress intensity factor of intelligent material by photoelastic experiment is introduced. In the mode I state, we can know that stress intensity factors are decreased more than 50% of stress intensity factor of room temperature when temperature of fiber is greater than 4$0^{\circ}C$, prestrain greater than 5% and fiber volume ratio greater than 0.42% and that stress intensity factors are decreased by 100% when fiber volume ratio is greater than 0.84%, prestrain greater than 5% and temperature greater than 60 $^{\circ}C$.

• Steel and Composite Structures
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• v.13 no.2
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• pp.187-206
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• 2012

In this study, fracture analysis of orthotropic FGM (Functionally Graded Material) plate having center crack is performed, numerically. Material axis arbitrarily oriented and there is an angle ${\theta}^{\circ}$ between material and crack axes. Stress intensity factors at the crack tips for Mode I are calculated using Displacement Correlation Method (DCM). In numerical analysis, effects of material properties and variation of angle ${\theta}^{\circ}$ between material and crack axes on the fracture behavior are investigated for four different boundary conditions. Consequently, it is found that the effect of ${\theta}^{\circ}$ on stress intensity factor depends on variation of material properties.